scholarly journals An Experimental Study of Bond Behavior of Micro Steel Fibers Added Self-compacting Concrete with Steel Reinforcement

2020 ◽  
Author(s):  
Abdul Salam ◽  
Shah Room ◽  
Shahid Iqbal ◽  
Khalid Mahmood ◽  
Qaiser Iqbal
Keyword(s):  
Bond Strength ◽  
Steel Fibers ◽  
Self Compacting Concrete ◽  
Bond Failure ◽  
Maximum Increase ◽  
Bond Behavior ◽  
Micro Cracks ◽  
Steel Bar ◽  
Experimental Values ◽  
Major Emphasis

The obstruction offered by the surrounding concrete to the pulling out of embedded steel bar is known as bond strength. Steel fibers addition to concrete improves its bond strength by arresting the cracks due to their bridging effect. Bond failure occurs when cracks in the surrounding concrete initiates, providing enough space for bar to be pulled-out. Micro steel fibers efficiently control the formation of micro cracks and may improve bond strength to a greater extent compared to the longer steel fibers. However, it reduces the workability of concrete which is of greater importance in case of self-compacting concrete (SCC). Reduction of workability is less pronounced when straight micro steel fibers are used due to their shorter lengths and straight geometry. Thus, different amount of straight micro steel fibers (0.25 %, 0.5 %, 0.75 %) were incorporated in to SCC to investigate their fresh and mechanical properties with major emphasis on the bond strength. Results indicate that steel fibers addition to SCC improve the splitting tensile strength and bond strength significantly with a maximum increase of 33.5 % and 54.9 % respectively with 0.75 % fibers addition. An equation is proposed for the calculation of bond strength with micro steel fibers addition to SCC with a maximum variation of 4 % to those of experimental values.

Beam Test Research on Bond Behavior between Steel Bar and Concrete in Salt-Frost Environment

2011 ◽  
Vol 261-263 ◽  
pp. 50-55
Author(s):  
Gang Xu ◽  
Tian Cheng Ai ◽  
Qing Wang ◽  
Jiang Bo Huang
Keyword(s):  
Bond Strength ◽  
Concrete Beam ◽  
Saline Solution ◽  
Freezing And Thawing ◽  
Bond Failure ◽  
Actual Structure ◽  
Bond Behavior ◽  
Steel Bar ◽  
Bond Property ◽  
Freezing And Thawing Cycles

Salt-frost action is one of the main causes that induced the decrease of force resistance behavior of concrete structure in cold areas. By the freezing and thawing cycles of 0, 50, 100 and 200 times for the reinforcement concrete beam specimens in saline solution, the effects of freezing and thawing cycles on the bond behavior between steel bar and concrete are studied. The results show that: with the increase of freezing and thawing cycles, the bond strength and the bond stiffness trend to degenerate. The co-operating capacity between steel bar and concrete falls down. The ductility of the specimens reduces, and the bond failure presents brittle. The degradation speed of bond strength after salt-frosting is relevant to the size and stirrup ratio of specimens, the larger the specimen’s size is, and the higher the stirrup ratio is, The stronger the capacity of resisting freezing-thawing cycle is, the more slowly the bond property degenerate, the study using small specimens will probably underestimate the frost resistance of actual structure.

Investigation of bond between lap-spliced steel bar and self-compacting concrete: The role of silica fume

2010 ◽  
Vol 37 (3) ◽  
pp. 420-428 ◽  
Author(s):  
Mehmet Karatas ◽  
Kazim Turk ◽  
Zulfu C. Ulucan
Keyword(s):  
Bond Strength ◽  
Silica Fume ◽  
Full Scale ◽  
Reinforcing Bars ◽  
Self Compacting Concrete ◽  
Normal Concrete ◽  
Steel Bar ◽  
Normalized Bond Strength ◽  
Constant Moment

In this study, normal concrete (NC) and four types of self-compacting concrete (SCC), in which cement was partially replaced by 5%, 10%, 15%, and 20% of silica fume (SF), were used to evaluate the effect of SF content on the bond strength of tension lap-spliced bars embedded in NC and SCC specimens. Therefore, 15 full-scale beam specimens (2000 × 300 × 200 mm3) were tested and 20 mm reinforcing bars were used with a 300-mm splice length as tension reinforcement. Each beam was designed with bars spliced in a constant moment region at midspan. It was found that the bond strength of the reinforcement embedded in SCC beams was higher than that of the reinforcement in NC beams, whilst the bond strength increased with increase in the replacement of cement by SF from 5% to 10%. Moreover, the beam specimens produced from SCC containing 5% SF had the highest normalized bond strength of 1.07 followed by SCC beams with 10% SF, 15% SF, NC beams, and 20% SF.

scholarly journals Effect of Coating Thickness on Bond Behaviors of Polymer Cement Coated Plain Steel Bar with Concrete and Finite Element Modeling

2016 ◽  
Vol 10 (1) ◽  
pp. 571-577 ◽  
Author(s):  
Xiong Yuanliang ◽  
Wang Kunrong ◽  
Liu Zhiyong ◽  
Yang Zhengguang
Keyword(s):  
Finite Element ◽  
Bond Strength ◽  
Coating Thickness ◽  
Failure Modes ◽  
Bond Behavior ◽  
Finite Element Software ◽  
Pullout Tests ◽  
Steel Bar ◽  
Contact Surfaces ◽  
Hot Rolled

The pullout tests were carried out to investigate the effect of coating thickness on bond behavior (failure modes, bond strength, bond stress slip curves) between hot rolled plain steel bar (HPB) coated with polymer cement based coating and concrete. The results indicated the failure mode of the specimens is pullout. Suitable coating thickness could enhance the bond strength of steel bar embedded with concrete. By using contact surfaces with cohesive behavior in finite element software, the slip between coated plain steel bar and concrete can be realized. The results of numerical simulation are close to that of experiments, indicating that the model using contact surfaces with cohesive behavior can reasonably predict the results of pullout tests of HPB in concrete.

scholarly journals Effect of Fibers on the Bond Behavior of Deformed Steel Bar Embedded in Recycled Aggregate Concrete

2020 ◽  
Vol 39 (4) ◽  
pp. 846-858
Author(s):  
Rashid Hameed ◽  
Usman Akmal ◽  
Qasim S. Khan ◽  
Muhammad Ahsan Cheema ◽  
Muhammad Rizwan Riaz
Keyword(s):  
Compressive Strength ◽  
Concrete Structures ◽  
Steel Fibers ◽  
Recycled Aggregates ◽  
Polypropylene Fibers ◽  
Reinforcing Bars ◽  
Bond Behavior ◽  
Pull Out ◽  
Steel Bar ◽  
Natural Aggregates

A large volume of concrete debris is being produced in many countries on the globe due to the demolition of old concrete structures and testing of concrete specimens in laboratories. One of the ways to reuse concrete debris is to produce Recycled Aggregates (RA) and use them in new concrete. In recent years, Recycled Aggregates Concrete (RAC) has experienced increasing demand in various non-structural and structural applications. In reinforced concrete structures, one of the sources of brittle failure is sudden loss of bond between reinforcing bars and concrete in anchorage zones. Therefore, for the structural application of any new kind of concrete such as fiber reinforced RAC, knowledge of bond characteristics of reinforcing bars embedded in concrete becomes essential for determining the overall structural response under different modes of loading. In this regard, this study experimentally investigated the effect of fibers on the bond stress-slip behavior of deformed steel re-bar embedded in RAC. Concrete mixes having 0, 50 and 100% RAs were prepared with and without the addition of fibers. Two types of fibers were investigated in mono form: hooked-ends steel and polypropylene fibers. The dosage of steel and polypropylene fibers was kept 40 and 4.4 kg/m3, respectively. Axial compression and standard pull-out tests were performed. Test specimens for pull-out test were prepared using deformed steel re-bars of 19mm (#6) diameter. The results of strength tests confirmed that the compressive strength of concrete is decreased by replacing Natural Aggregates (NA) with RAs. For bond behavior of steel re-bar, the results of this study showed that replacement of 50% NA with RAs did not affect the bond response of steel bar, however, 100% replacement of NA with RAs showed detrimental effect on bond stress slip behavior. The results further showed that the addition of both types of fibers made it possible to recover the loss in compressive strength, bond strengths and bond toughness occurred because of replacing NA with RAs. In case of RA concrete mixes containing hooked-ends steel fibers, strength values were found even greater than the strength values of Natural Aggregates Concrete (NAC). From the results of this study, it was found that it is possible to design a structural concrete mix using 100% RAs and steel fibers at relatively low dosage of 40kg/m3.

scholarly journals Finite element analysis on the bond behavior of steel bar in salt–frost-damaged recycled coarse aggregate concrete

2021 ◽  
Vol 60 (1) ◽  
pp. 853-861
Author(s):  
Tian Su ◽  
Ting Wang ◽  
Haihe Yi ◽  
Rui Zheng ◽  
Yizhe Liu ◽  
...  
Keyword(s):  
Bond Strength ◽  
Concrete Cover ◽  
Bond Slip ◽  
Bond Behavior ◽  
Steel Bar ◽  
Calculation Results ◽  
Cover Thickness ◽  
Bar Diameter ◽  
Good Agreement ◽  
Ultimate Bond Strength

Abstract In this article, the ABAQUS finite element software is used to simulate the bond behavior of the steel bar in salt–frost-damaged recycled coarse aggregate concrete, and the influence of the steel bar diameter and the concrete cover thickness on the bond strength is investigated. The result shows that the calculated bond–slip curve is in good agreement with the experimental bond–slip curve; the mean value of the ratio of the calculation results of ultimate bond strength to the experiment results of ultimate bond strength is 1.035, the standard deviation is 0.0165, and the coefficient of variation is 0.0159, which proves that the calculation results of the ultimate bond strength are in good agreement with the experimental results; with the increase of steel bar diameter and the concrete cover thickness, the ultimate bonding strength of RAC and steel increases; the calculation formulas for the ultimate bond strength of specimens with different steel bar diameters (concrete cover thickness) after different salt–frost cycles are obtained.

scholarly journals A study of the bond behavior of FRP bars in MPC seawater concrete

2020 ◽  
pp. 136943322095681
Author(s):  
Wen Sun ◽  
Yu Zheng ◽  
Linzhu Zhou ◽  
Jiapeng Song ◽  
Yun Bai
Keyword(s):  
Bond Strength ◽  
Potassium Phosphate ◽  
Fiber Reinforced Polymer ◽  
Reinforcing Bars ◽  
Bond Behavior ◽  
Reinforced Polymer ◽  
Steel Bar ◽  
Gfrp Bar ◽  
Frp Bar ◽  
Frp Bars

Using magnesium potassium phosphate cement (MPC) and fiber-reinforced polymer (FRP) bar to produce reinforced concrete can overcome the durability problems facing conventional steel reinforced PC concrete. In addition, FRP bar reinforced MPC concrete can also mitigate the CO2 emission issues caused by Portland cement (PC) production and the shortage of natural resources such as virgin aggregates and freshwater. This paper, therefore, is aimed at investigating the bond behavior of the FRP bars in MPC seawater concrete. The direct pullout tests were conducted with a steel bar, BFRP bar, and GFRP bar embedded into different concretes. The effects of reinforcing bars, type of concrete and mixing water on the bond behavior of FRP and steel bars were investigated and discussed. The results showed that the MPC concrete increases the bond strength of BFRP and GFRP bars by 51.06% and 24.42%, respectively, compared with that in PC concrete. Using seawater in MPC concrete can enhance the bond strength of GFRP bar by 13.75%. The damage interface of the FRP bar -MPC is more severe than that of PC with a complete rupture of the FRP ribs and peeling-off of the resin compared to that in steel reinforced MPC specimens. Moreover, the bond stress-slip models were developed to describe the bond behavior of MPC-FRP specimen, and the analytical results match well with the experimental data. In conclusion, the FRP bars showed better bond behavior in the MPC seawater concrete than that in the PC counterparts.

Effect of Elevated Temperature on Bond Strength of Concrete

2019 ◽  
Vol 972 ◽  
pp. 26-33
Author(s):  
Muhammad Harunur Rashid ◽  
Md. Maruf Molla ◽  
Imam Muhammad Taki
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperature ◽  
Bond Strength ◽  
Elevated Temperatures ◽  
Reinforced Concrete Structure ◽  
Bond Behavior ◽  
Pull Out ◽  
Steel Bar ◽  
Residual Capacity ◽  
Water Curing

In the case of exposure of reinforced concrete structure to accidental fire, an assessment of its residual capacity is needed. Bond strength of concrete was observed under elevated temperatures (150°, 250°, 350° and 500°C) in this study. Cylindrical specimens were prepared for pull-out tests to find out the bond behavior and to observe the mechanical properties of concrete. All the specimens were 100 mm diameter and 200 mm height. The pull-out specimens contain a 10 mm steel bar at its center. The specimens were tested at 52 days age following a 28 days water curing. Samples were preheated for 3 hours at 100°C temperature and then put into the furnace for 1 hour at the target temperature. Samples were tested before preheating as controlled specimens. In case of mechanical properties and the bond strength of concrete, there were no remarkable changes due to elevated temperature up to 150°C. However, the mechanical properties and bond strength were decreased gradually after 150°C temperature. Maximum reduction of bond strength observed was 52.13% and 49.8% at 500°C for testing within 1 hour and after 24 hours of heating respectively when compared to the controlled specimens. Bond strength was found to reduce at a greater rate than compressive strength due to the elevated temperature.

scholarly journals Bond behavior of self compacting concrete

2018 ◽  
Vol 13 (s1) ◽  
pp. 95-105
Author(s):  
S. Ponmalar
Keyword(s):  
Construction Industry ◽  
Load Transfer ◽  
Mechanical Vibration ◽  
Interfacial Transition Zone ◽  
Bond Stress ◽  
Self Compacting Concrete ◽  
Normal Concrete ◽  
Bond Behavior ◽  
Steel Bar ◽  
Bottom Side

Abstract The success of an optimum design lies in the effective load transfer done by the bond forces at the steel-concrete interface. Self Compacting Concrete, is a new innovative concrete capable of filling intrinsic reinforcement and gets compacted by itself, without the need of external mechanical vibration. For this reason, it is replacing the conventional vibrated concrete in the construction industry. The present paper outlays the materials and methods adopted for attaining the self compacting concrete and describes about the bond behavior of this concrete. The bond stress-slip curve is similar in the bottom bars for both SCC and normal concrete whereas a higher bond stress and stiffness is experienced in the top and middle bars, for SCC compared to normal concrete. Also the interfacial properties revealed that the elastic modulus and micro-strength of interfacial transition zone [ITZ] were better on the both top and bottom side of horizontal steel bar in the SCC mixes than in normal vibrated concrete. The local bond strength of top bars for SCC is about 20% less than that for NC. For the bottom bars, however, the results were almost the same.

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